A spectrometry system in general includes an ion source for ionizing components of a sample of interest, an analyzer for separating the ions based on a discriminating attribute, an ion detector for counting the separated ions, and electronics for processing output signals from the ion detector as needed to produce user-interpretable spectral information. In a mass spectrometry (MS) system, the analyzer is a mass analyzer that separates the ions based on their differing mass-to-charge ratios (or m/z ratios, or more simply “masses”). Depending on design, the mass analyzer may separate ions by utilizing electric and/or magnetic fields, or time-of-flight tubes. The mass analyzer is maintained at low vacuum in a manifold (or housing, chamber, etc.). In an ion mobility spectrometry (IMS) system, the analyzer is a drift cell that separates ions based on their different cross-sectional areas. The drift cell is enclosed in a manifold that in some IM techniques may be maintained a vacuum level in the range of, for example, 1 to 5 Torr. IM separation occurs as ions travel a known distance through a known environment of drift gas at a known pressure, which may be a vacuum level in the range of, for example, 1 to 5 Torr. Ions of differing cross-sectional areas have differing mobilities through the gas environment. Ions are pulled through the drift cell by a DC voltage gradient. Typical electric fields utilized in a low-field IMS technique range from, for example, 10 to 20 V/cm. An IMS may be coupled with an MS to provide unique two-dimensional information about an analyte under investigation. All such systems may further include other types of ion processing devices (e.g., ion guides) that include ion optics enclosed in vacuum stages and operating at high voltages.
Working with high voltages in a vacuum in the range of 1 to 10 Torr can be particularly challenging due to the increased susceptibility of voltage breakdown, which can adversely affect the operation of an ion processing or analyzing device. This is a well-known phenomenon described by the equations of the Paschen Curve for various gases (e.g., hydrogen, helium, nitrogen, noble gases). Generally, the breakdown voltage required to cause an electrical discharge or arc between two electrodes is a function of gas pressure and the spacing (gap distance) between the electrodes. Prior solutions for overcoming the problem of voltage breakdown include enclosing the high voltage elements in an insulating structure inside a metal vacuum manifold, or increasing the spacing between the high voltage elements and the vacuum manifold, or constructing the vacuum manifold from insulating materials. The prior solutions result in increased cost and large, bulky, and often unreliable vacuum manifold structures.
Therefore, there remains an ongoing need for ion processing devices and systems utilizing vacuum manifolds configured and/or operated to better address the problem of voltage breakdown.